Intro To Flex PCBs

Picture of a Flex Board Sierra Circuits

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If you have been a regular user of electronic devices at any point in the past 30 years—or have just looked up at the procession of phones, laptops, and MP3 players—you have likely noticed some dramatic design changes. For starters, many of these devices have gotten progressively smaller.

Innovations like flexible PCBs offer significant amounts of design freedom, so products can be both lightweight and durable, as well as assembled as part of a streamlined and highly efficient economy of scale. With that in mind, let’s look at how flex PCBs differ from rigid PCBs and how they can enable a wide range of advantages—from more compact devices to fewer errors during manufacturing.

Flex PCB 101
As the name suggests, flex PCBs are flexible circuits with very thin substrates and high levels of bendability, tensile strength, and physical flexibility. They can also be molded into complex three-dimensional shapes for use across a diverse range of applications, such as heads-up displays for aerospace piloting, wearable technology, and miniscule devices (e.g., modern hearing aids) for medical care.

The material used in flex PCBs can be just a few microns thick, yet still be reliably etched. This often makes them preferable to rigid PCBs in certain applications, in addition to the benefit of removing traditional wiring harnesses and ribbon connectors, in particular contexts.

For example, a flex PCB can be routed at tough angles within the tight confines of a device such as a satellite, while still sporting a sufficiently high conductor density. This adaptability is not possible when using ribbon cables. Moreover, flex PCBs unlock many physical design advantages, including:

  • 360-degree bendability.
  • Superior resistance to vibrations and other disruptions within harsh environments.
  • Support for compact, lightweight design; product weight can be greatly reduced.
  • Small, flexible cables that take up less space than typical wires.
  • The ability to be warped or contorted without any associated breakage.

On the manufacturing side, flex PCBs are similarly advantageous. They permit better airflow and heat dissipation than many other PCBs. Their modest counts of interconnections and components also mean that their assembly costs are much lower than those for traditional wiring harnesses. Plus, there is less overall susceptibility to assembly error, since the manufacturing process is streamlined and standardized, without the problematic manual input required for building many of these harnesses.

Flex PCBs are often the best choice for connecting complex electronics internal systems. Flexible circuits are ideal for devices within the aerospace, medical and consumer technology fields, as they are more versatile and—dare we say—flexible than their rigid alternatives. Thinner, more compact products are an obvious result of flexible circuits as well.

For more information, check out our flex PCB pages, and download our flex PCB design guide.

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